1. Field of the Invention
The present invention relates to an emulsion, and in particular, relates to an oil-in-water emulsion for encapsulating paclitaxel.
2. Description of the Related Arts
Paclitaxel is a polyhydroxyl compound extracted from Texus brevifolia, and an effective anti-cancer drug. The major mechanism of the anti-cancer activity of the paclitaxel involves stabilizing microtubulin to inhibit the mitosis of tumor cells. Recently, many studies of paclitaxel in phase I and phase II clinical trials have been conducted. Furthermore, the paclitaxel has passed the phase III clinical trial against refractory ovarian cancer, breast cancer and melanoma cancer, and has been applied in the therapies thereof.
However, paclitaxel has low solubility in water (about 0.01 mg/ml) and no therapeutic effect if administrated orally. Thus, a suitable drug delivery system for administration is required. In clinical applications, paclitaxel is dissolved in Diluent 12, which is a carrier composed of 50% polyethoxylated castor oil (Cremophor EL) and 50% absolute ethanol, and then administrated to patients. Cremophor EL can cause hypersensitivity and may crystallize during the process of dilution.
To address the disadvantage of Diluent 12, many carriers used in injection administrations have been developed in recent years. Examples of these carriers are oil-in-water emulsion, liposome, and non-ionic surfactant micelles. As oil-in-water emulsions are bio-degradable, bio-compatible, easy for mass production and less toxic, they have been the preferred candidate for the delivery system. It is known that the above oil-in-water emulsion systems can form a more stable lipid emulsion, which is useful for encapsulating lipophilic drug, if phospholipid is added thereto. The oil-in-water emulsion functions as a vector for administration to prolong the drug-releasing rate in blood. However, a conventional oil-in-water emulsion can be absorbed easily by the endoreticular system within the body and destroyed. Accordingly, the lipophilic drug cannot be maintained at a constantly effective concentration in blood, and thus the conventional oil-in-water emulsion is not stable.
It is therefore an object of the present invention to provide an oil-in-water emulsion for encapsulating paclitaxel that can eliminate the disadvantages of the conventional oil-in-water emulsions.
The above object of the invention is attained by using an emulsion including triglyceride and emulsifier. The emulsifier includes phosphatidyl choline, non-ionic surfactant and polyethyleneglycol-modified phosphatidylethanolamine. Optionally, the emulsion of the invention can further include a pharmaceutically acceptable aqueous solution.
The surface of the oil-in-water emulsion is modified by the polyethyleneglycol-modified disteaoyl phosphatidylethanolamine, and thus the lipid emulsion has excellent paclitaxel-encapsulating ability and is stable in blood.